A119101 - OEIS

%I #10 Mar 22 2023 10:53:36

%S 1,15,21,55,1225,2211,5151,15225,21115,22155,151525,222111,255255,

%T 11551221,12552555,21115251,22221111,51151555,111221155,251115255,

%U 2222211111,2552515525,111251152551,122515222515,222222111111,1125152255151,2522551111515,5255121522225

%N Triangular numbers composed of digits {1,2,5}.

%H Giovanni Resta, <a href="http://www.numbersaplenty.com/tr/tr125.html">Tridigital Triangular Numbers</a>

%F a(n) = A000217(A119102(n)). - _Michel Marcus_, Mar 22 2023

%Y Cf. A000217, A031153, A119102. See A119033 for a table of cross-references.

%K nonn,base

%O 1,2

%A _Giovanni Resta_, May 10 2006

%E a(26)-a(28) from _Tyler Busby_, Mar 22 2023